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[/] [neorv32/] [trunk/] [rtl/] [core/] [neorv32_wdt.vhd] - Rev 64
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-- ################################################################################################# -- # << NEORV32 - Watch Dog Timer (WDT) >> # -- # ********************************************************************************************* # -- # Watchdog counter to trigger an action if the CPU gets stuck. # -- # The internal counter is 20-bit wide. If this counter overflows one of two possible actions is # -- # triggered: Generate an IRQ or force a hardware reset of the system. # -- # A WDT action can also be triggered manually at any time by setting the FORCE bit. # -- # # -- # Access to the control register can be permanently locked by setting the lock bit. This bit # -- # can only be cleared by a hardware reset (external or caused by the watchdog itself). # -- # ********************************************************************************************* # -- # BSD 3-Clause License # -- # # -- # Copyright (c) 2021, Stephan Nolting. All rights reserved. # -- # # -- # Redistribution and use in source and binary forms, with or without modification, are # -- # permitted provided that the following conditions are met: # -- # # -- # 1. Redistributions of source code must retain the above copyright notice, this list of # -- # conditions and the following disclaimer. # -- # # -- # 2. Redistributions in binary form must reproduce the above copyright notice, this list of # -- # conditions and the following disclaimer in the documentation and/or other materials # -- # provided with the distribution. # -- # # -- # 3. Neither the name of the copyright holder nor the names of its contributors may be used to # -- # endorse or promote products derived from this software without specific prior written # -- # permission. # -- # # -- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS # -- # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF # -- # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE # -- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, # -- # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE # -- # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED # -- # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING # -- # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED # -- # OF THE POSSIBILITY OF SUCH DAMAGE. # -- # ********************************************************************************************* # -- # The NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting # -- ################################################################################################# library ieee; use ieee.std_logic_1164.all; use ieee.numeric_std.all; library neorv32; use neorv32.neorv32_package.all; entity neorv32_wdt is port ( -- host access -- clk_i : in std_ulogic; -- global clock line rstn_i : in std_ulogic; -- global reset line, low-active addr_i : in std_ulogic_vector(31 downto 0); -- address rden_i : in std_ulogic; -- read enable wren_i : in std_ulogic; -- write enable data_i : in std_ulogic_vector(31 downto 0); -- data in data_o : out std_ulogic_vector(31 downto 0); -- data out ack_o : out std_ulogic; -- transfer acknowledge -- clock generator -- clkgen_en_o : out std_ulogic; -- enable clock generator clkgen_i : in std_ulogic_vector(07 downto 0); -- timeout event -- irq_o : out std_ulogic; -- timeout IRQ rstn_o : out std_ulogic -- timeout reset, low_active, use as async ); end neorv32_wdt; architecture neorv32_wdt_rtl of neorv32_wdt is -- IO space: module base address -- constant hi_abb_c : natural := index_size_f(io_size_c)-1; -- high address boundary bit constant lo_abb_c : natural := index_size_f(wdt_size_c); -- low address boundary bit -- Control register bits -- constant ctrl_enable_c : natural := 0; -- r/w: WDT enable constant ctrl_clksel0_c : natural := 1; -- r/w: prescaler select bit 0 constant ctrl_clksel1_c : natural := 2; -- r/w: prescaler select bit 1 constant ctrl_clksel2_c : natural := 3; -- r/w: prescaler select bit 2 constant ctrl_mode_c : natural := 4; -- r/w: 0: WDT timeout triggers interrupt, 1: WDT timeout triggers hard reset constant ctrl_rcause_c : natural := 5; -- r/-: cause of last action (reset/IRQ): 0=external reset, 1=watchdog overflow constant ctrl_reset_c : natural := 6; -- -/w: reset WDT if set constant ctrl_force_c : natural := 7; -- -/w: force WDT action constant ctrl_lock_c : natural := 8; -- r/w: lock access to control register when set -- access control -- signal acc_en : std_ulogic; -- module access enable signal wren : std_ulogic; signal rden : std_ulogic; -- control register -- type ctrl_reg_t is record enable : std_ulogic; -- 1=WDT enabled clk_sel : std_ulogic_vector(2 downto 0); mode : std_ulogic; -- 0=trigger IRQ on overflow; 1=trigger hard reset on overflow rcause : std_ulogic; -- cause of last system reset: '0' = external, '1' = watchdog reset : std_ulogic; -- reset WDT enforce : std_ulogic; -- force action lock : std_ulogic; -- lock control register end record; signal ctrl_reg : ctrl_reg_t; -- prescaler clock generator -- signal prsc_tick : std_ulogic; -- WDT core -- signal wdt_cnt : std_ulogic_vector(20 downto 0); signal hw_rst : std_ulogic; signal rst_gen : std_ulogic_vector(03 downto 0); -- internal reset (sync, low-active) -- signal rstn_sync : std_ulogic; begin -- Access Control ------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- acc_en <= '1' when (addr_i(hi_abb_c downto lo_abb_c) = wdt_base_c(hi_abb_c downto lo_abb_c)) else '0'; wren <= acc_en and wren_i; rden <= acc_en and rden_i; -- Write Access --------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- write_access: process(rstn_i, clk_i) begin if (rstn_i = '0') then ctrl_reg.reset <= '0'; ctrl_reg.enforce <= '0'; ctrl_reg.enable <= '0'; -- disable WDT ctrl_reg.mode <= '0'; -- trigger interrupt on WDT overflow ctrl_reg.clk_sel <= (others => '1'); -- slowest clock source ctrl_reg.lock <= '0'; elsif rising_edge(clk_i) then if (rstn_sync = '0') then -- internal reset ctrl_reg.reset <= '0'; ctrl_reg.enforce <= '0'; ctrl_reg.enable <= '0'; -- disable WDT ctrl_reg.mode <= '0'; -- trigger interrupt on WDT overflow ctrl_reg.clk_sel <= (others => '1'); -- slowest clock source ctrl_reg.lock <= '0'; else -- auto-clear WDT reset and WDT force flags -- ctrl_reg.reset <= '0'; ctrl_reg.enforce <= '0'; -- actual write access -- if (wren = '1') then ctrl_reg.reset <= data_i(ctrl_reset_c); ctrl_reg.enforce <= data_i(ctrl_force_c); if (ctrl_reg.lock = '0') then -- update configuration only if unlocked ctrl_reg.enable <= data_i(ctrl_enable_c); ctrl_reg.mode <= data_i(ctrl_mode_c); ctrl_reg.clk_sel <= data_i(ctrl_clksel2_c downto ctrl_clksel0_c); ctrl_reg.lock <= data_i(ctrl_lock_c); end if; end if; end if; end if; end process write_access; -- clock generator -- clkgen_en_o <= ctrl_reg.enable; -- enable clock generator prsc_tick <= clkgen_i(to_integer(unsigned(ctrl_reg.clk_sel))); -- clock enable tick -- Watchdog Counter ----------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- wdt_counter: process(clk_i) begin if rising_edge(clk_i) then if (ctrl_reg.reset = '1') then -- watchdog reset wdt_cnt <= (others => '0'); elsif (ctrl_reg.enable = '1') and (prsc_tick = '1') then wdt_cnt <= std_ulogic_vector(unsigned(wdt_cnt) + 1); end if; end if; end process wdt_counter; -- action trigger -- irq_o <= ctrl_reg.enable and (wdt_cnt(wdt_cnt'left) or ctrl_reg.enforce) and (not ctrl_reg.mode); -- mode 0: IRQ hw_rst <= ctrl_reg.enable and (wdt_cnt(wdt_cnt'left) or ctrl_reg.enforce) and ( ctrl_reg.mode); -- mode 1: RESET -- Reset Generator & Action Cause Indicator ----------------------------------------------- -- ------------------------------------------------------------------------------------------- reset_generator: process(rstn_i, clk_i) begin if (rstn_i = '0') then ctrl_reg.rcause <= '0'; rst_gen <= (others => '1'); -- do NOT fire on reset! rstn_sync <= '1'; elsif rising_edge(clk_i) then ctrl_reg.rcause <= ctrl_reg.rcause or hw_rst; -- sticky-set on WDT timeout/force if (hw_rst = '1') then rst_gen <= (others => '0'); else rst_gen <= rst_gen(rst_gen'left-1 downto 0) & '1'; end if; rstn_sync <= rst_gen(rst_gen'left); end if; end process reset_generator; -- system reset -- rstn_o <= rst_gen(rst_gen'left); -- Read Access ---------------------------------------------------------------------------- -- ------------------------------------------------------------------------------------------- read_access: process(clk_i) begin if rising_edge(clk_i) then ack_o <= rden or wren; if (rden = '1') then data_o(ctrl_enable_c) <= ctrl_reg.enable; data_o(ctrl_mode_c) <= ctrl_reg.mode; data_o(ctrl_rcause_c) <= ctrl_reg.rcause; data_o(ctrl_clksel2_c downto ctrl_clksel0_c) <= ctrl_reg.clk_sel; data_o(ctrl_lock_c) <= ctrl_reg.lock; else data_o <= (others => '0'); end if; end if; end process read_access; end neorv32_wdt_rtl;
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